There is no way to remove bytes from the middle of a file without rewriting it, and there is no way to rewrite it without reading it. However, 500MiB is really nothing, unless you need to access it over a (slow) network or very slow local media such as tape, which is thankfully, finally becoming less common. With typical consumer-level HDDs from a few years ago, you're probably looking at a few seconds.

The basic structure would be something like this:

    while (<>) {
        print unless /^pattern to skip$/;
    }
[download]

If you need to do something based on line number, use $. to get the current line number.

This also leads itself fairly readily to a one-liner if your logic is relatively simple:

    $ perl -nle 'print unless /^pattern to skip$/ or $. == 10' filename.txt

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.